The present invention relates to semiconductor-on-insulator (SOI) devices and methods for fabricating the same. More particularly, the body of a semiconductor-on-insulator device is tied to the grounded substrate to improve threshold voltage control and reduce history effects. The body is grounded without a so-called Tbody or Hbody contact scheme. This new body contact structure reduces the high parasitic capacitance associated with conventional body contacts.
Silicon-on-insulator (SOI) technology has become an increasingly important technique utilized in the fabrication and production of semiconductor devices. SOI technology deals with the formation of transistors in a relatively thin mono crystalline semiconductor layer, which overlays an insulating layer. In other words, the active devices are formed in a thin semiconductor disposed on an insulator layer rather than in the bulk semiconductor of the device.
In a typical SOI transistor, the body is generally isolated from the silicon substrate and usually kept floating. This may result in problems for current-sensitive circuit applications, since the body typically retains charge from the previous time the transistor was utilized. The retained charge within the body interferes with subsequent use of the device. A variety of solutions have been proposed to address the problems associated with the SOI semiconductor device. For example, the use of a body contact in the SOI device addresses this problem, and also allows the threshold voltage to be changed so that standby power can be reduced for low-power applications. The body contact in the SOI device has conventionally been made by the use of a T-shaped or a H-shaped polysilicon structure on an active area, thereby creating three distinct regions including a source region, a drain region, and a body contact region.
However, the T-shaped or H-shaped polysilicon structure layout cost area and increase the power dissipated in the circuit.